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By Patricia Reaney
LONDON
(Reuters) - A new vaccine that protects monkeys against
the deadly Ebola virus could lead to the development of
a similar one for humans, scientists said on Wednesday.
Ebola
is a terrifying disease that causes high fever, massive
internal bleeding and death usually within seven to 21 days
of infection. It strikes quickly and unexpectedly and kills
90 percent of its victims. Hundreds of people have died
in recent outbreaks.
A team
of scientists, led by researchers at the National Institutes
of Health (NIH) in the United States, has successfully vaccinated
four monkeys against what would be a lethal dose of the
virus.
``We
don't know if this model perfectly replicates what happens
in humans. It remain an open question whether this vaccine
strategy will be successful in humans,'' Gary Nabel, of
the Dale and Betty Bumpers Vaccine Research Center at the
NIH, said in a telephone interview.
``It
will serve as a model to give us the scientific information
that we need to learn how to develop the vaccine,'' he said.
Three
Strains Of Ebola Virus
The
vaccine uses strains of DNA containing genes that encode
Ebola virus proteins to induce an immune response. The researchers
also boosted that response by including a weakened strain
of a different virus in the vaccine.
Nabel
and his team, whose research is published in the science
journal Nature, said the four monkeys injected with the
vaccine were protected from the virus and were still free
of infection six months later.
``Ebola
is a difficult virus because currently available antiviral
drugs have no proven effect on it and we do not know its
natural reservoir, making environmental control impossible,''
said Dr Anthony Fauci, director of the National Institute
of Allergy and Infectious Diseases at the NIH.
``A
vaccine is therefore the best hope for protecting humans
from infection, and this study makes some key advances toward
realizing that goal,'' he said.
A human
vaccine will have to protect against the three known fatal
Ebola strains -- Zaire, Sudan and Ivory Coast.
The
vaccine tested on the monkeys includes genes encoding proteins
from the three strains of the virus.
``We
of course want to test the multivalent vaccine for effectiveness
against all three strains of Ebola but we also need to look
more closely at the immune response induced by these vaccine
so we can nail down what is needed for protection,'' said
Dr Nancy Sullivan, who worked on the project.
The
Ebola virus was first identified in 1976. It emerged from
an unknown source, which scientists suspect was an animal,
and caused outbreaks in Sudan and the former Zaire.
Isolated
outbreaks have occurred since then, most recently in Uganda
where the Sudan strain had killed 129 people, as of November
24.
The
virus is extremely infectious and spread through direct
physical contact. It can be transmitted through a handshake,
coughing or sneezing.
``Time
will tell whether this is a vaccine that has success in
people. The results of the study encourage us to pursue
this as a vaccine candidate in humans,'' Nabel said.
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